...or start by taking a quick course on EFI Fuel System Conversion!

Congratulations! Taking the step to move from carburetion to Electronic Fuel
Injection (EFI) is commendable--and comes with some great rewards! But it does
require some upgrades to be made to your existing fuel system. We are frequently
asked what fuel pump and other components are required to make the carb to EFI
switch. This page sets out to answer those questions and give you a one-stop
shop to purchase the exact components you need to be successful!

How Do I Upgrade My Carburetor Fuel Pump?

The biggest difference between a fuel system for a carbureted engine and the
fuel system for an EFI engine is the pressure. Most carburetors want about 2-4
PSI at the inlet. Any more than that will push the fuel right past the needle
valve and flood fuel into the engine. To accomplish this, carbureted vehicles
use a much lower-pressure pump (you'll need to change that) and a non-return
style regulator (you'll need to change that too.) The non-return style fuel
pressure regulator simply holds back whatever few pounds of excess pressure is
supplied by the low-pressure fuel pump and only lets through what pressure is
required by the carburetor.

How Much Fuel Pump Do I Need?

Set aside the question of pressure for a moment--we'll get to that. The
question you need to ask at this point is, "How much fuel pump do I need?" That
is based on the amount of horsepower you expect your engine to make. We offer
EFI fuel pumps in several different flow ratings. These fuel pumps will feed
different amounts of horsepower based on whether the vehicle is carbureted or
uses force induction (turbo or supercharger) and the fuel that the engine uses
(gasoline or E-85.) Here is a chart to give you an idea:

Flow Rate(LPH)

Naturally AspiratedMax HP*

Force InductionMax HP*

155 LPH

400 HP

330 HP

190 LPH

500 HP

400 HP

255 LPH

670 HP

540 HP

450 LPH

1180 HP

950 HP

*All values shown for gasoline. Multiply by .72 to calculate the amount of
horsepower supported when using E85.

Inline or In-Tank Pump?

When converting from carbureted fuel system to EFI fuel system, inline is
generally the easy answer. Buy one of our inline EFI conversion kits, install
the pump as close to the tank and as low as possible. Ensure that you install
a filter before and after, and you are all set. You likely don't even need to
drop the fuel tank!

However, some folks just aren't happy with inline fuel pumps and want to go
in-tank. Maybe they need to run E85 (which is only compatible with the 450 LPH
in-tank pump) or they need more than 255 LPH (the maximum individual inline fuel
pump. In-tank pumps are, admittedly, a bit quieter (although the Walbro GSL-family of
inline fuel pumps are remarkably quiet for performance fuel pumps.) In that case
you need to be prepared to do a bit more engineering as a result of your choice.
Our in-tank EFI conversion kits include a in-tank pump along with a sock filter.
It is going to be necessary for you to use a wiring bulkhead (included in the
kit) to provide you with power in the tank for the pump. Then, you are going to
need to engineer some sort of holder to which to affix the fuel pump so that it
stays firmly in place, upright and at the bottom of the tank. Consult a
fabricator who has experience in this area if you have specific questions or
need assistance.

What Fuel Pressure Regulator Do I Need?

You will need a return-style fuel pressure regulator to deliver the correct
fuel pressure to the engine. Those are readily available. We recommend the
outstanding Holley HP EFI Adjustable Fuel Pressure Regulator. It is adjustable
from 15 to 65 PSI.

However, the intuitive reader will realize there is
currently only one fuel line between the fuel tank and the engine compartment.
That means that a second fuel line must be installed for virtually all EFI
fuel system upgrades. It is not necessary for the line to be metal (as is the OE
fuel line.) We recommend using a good quality EFI fuel hose that is available
at any auto parts store. It is left as an exercise to the installer to determine
the safest way to correctly secure the fuel line in place in a manner that
ensures that it is not crimped or kinked. An abundance of cable ties fixing the
hose to the OE metal line usually works well. Note that sometimes it is
advisable to use the metal line as the return and the hose as the feed. This is
particularly true when one is running an especially-high horsepower engine and
might be feeding two or even three fuel pumps into a single line. In this case,
source a larger hose to accommodate the large amount of fuel that will be needed.

Where Do I Return Fuel To The Tank?

The fuel tank that was installed in your carbureted vehicle likely made
no provision for fuel return. That being the case, this is another opportunity
for you to be creative. Many tanks have a vent that has been used by some
installers to attach the return line. We don't have enough experience to either
confirm or deny the efficiency of that method. However, on all of our kits we
offer the option of ordering a fuel line bulkhead. This allows you to drill a
hole in the top of the tank and insert through that a hose barb fitting. The
bulkhead fitting includes washers for both sides of the fuel tank and should
provide perfectly for your requirements.

Other Excellent Questions

What About Electrical Connections?

Because there can be such a broad range of electrical component requirements
we don't offer specific kits for this. These components are typically readily
available at most auto parts or hardware stores. We are happy to give you some
insight into the things you should consider when laying out your electrical
connections.

First and foremost, the fuel pump should never be wired to the ignition
switch. Virtually all EFI controllers will provide a 12-volt line
for the fuel pump. That line should be used to switch a standard 30-amp relay,
which in turn powers the fuel pump. The reason for this is that the controller
(ECU) knows when the engine is running and turns off power to the pump if the
engine is not running. The engine will quit running if the fuel line is cut,
which in turn will turn off the fuel pump. If you wire your fuel pump to the
ignition switch, it will continue to pump fuel out the cut line. Bad. Very
bad.

Always include a fuse in the power line to the pump. Here is some guidance on
suggested fuse and wire sizes for the various pumps included in our Carb to EFI conversion
kits. Note that wire gauges based on 15 feet of wire--increase gauge by 2 if
extending wire beyond 15 feet:

190 LPH, 255LPH and 450 LPH Pump: 20 Amp / 14 Gauge

155 LPH Pump: 15 Amp / 14 Gauge

155 LPH Lo Pressure TBI Pump: 5 Amp / 18 Gauge

Run a same-sized ground wire and fasten to the most solid grounding surface
you can reasonably find. Failure to adequately ground the pump will result
in reduced flow, increased power draw, potentially blowing fuses and shortening
fuel pump life. Don't get yourself in trouble because you figured just fastening
a 6-inch ground wire to the rusty frame nearest the fuel pump would be adequate.

What If I Use A Bigger Fuel Pump Than I Need?

Generally, it is fine to run a fuel pump that can supply more fuel than your
engine can consume as long as you don't ever use one that is inadequate. Running
a larger fuel pump usually means that the pump will be a bit louder and draw a
bit more amperage but if neither of those is an issue then it isn't a problem.
The only time that it could create a problem is if you run so much fuel pump that
the return line is too small to flow enough fuel back to the tank. Then your
fuel pressure would spike (regardless of the fuel pressure regulator) and more
fuel than is intended is delivered to the engine (resulting in bad things beyond
the scope of this article.)

Can I Run E85 Through These Pumps?

At this time, of the pumps listed only the 450 LPH in-tank pump (F20000267)
can operate with E85. The problem is lubricity. Alcohol provides virtually no
lubrication and, at 85% alcohol, E85 is an extremely harsh fluid to try to pump.
In addition, high concentrations of ethanol (above 10% found in most pump gases)
do other bad things to the internals of pumps that are not specifically rated
for E85. If you have any intention of running E85 then use the 450 LPH pump and
recognize that 450 LPH of E85 can only support 850 naturally-aspirated HP or 680
turbo or supercharged HP.

What If I'm Running Throttle Body Injection?

GM's fuel injected engines prior to 1996 were largely low-pressure
throttle-body injection (TBI). There is nothing wrong with these engines--not
only are many still in service but Holley and other manufacturers make
high performance throttle bodies for them. The key difference is the fuel
pressure. These TBI units require no more than about 12 PSI for normal
operation. If you are replacing your carbureted engine with one of these GM TBI
engines, it is imperative that you get a low-pressure pump and a fuel pressure
regulator suited for TBI pressures. Fortunately, we have kits for those too.
Our Carb to TBI conversion kit does not include a fuel pressure regulator since
one is built into the throttle body. If you require adjustable fuel pressure
then consider the JET 61500-series.

Note that we don't offer an in-tank pump kit for low-pressure / TBI
applications. This is because Walbro's largest-flowing low-pressure pump is only
115 LPH, which we figured would be too small for most applications. Instead,
choose the low-pressure / TBI inline pump kit that makes a solid 155 LPH at 12
PSI.

What About Filters?

Walbro high performance fuel pumps are incredibly durable but, because of the
incredibly tight tolerances that make this such a powerful pump, a single hard
bit of debris can effectively end its life. However, you don't have to worry
about that because all of our Carb to EFI conversion kits include both inlet
and outlet filters. In the event you are reading this and realize your pump
isn't running an inlet filter, you can remedy that by installing a filter of
no more than about 35 microns in front of the pump. You can go as fine as 20
microns (which we use) if the filter media is large enough that the filter does
not become plugged.

After the pump, it is necessary for there to be filtration to about 10 microns
before the fuel injectors. While it may seem intuitive to simply install a
single 10 micron filter before the pump and none after that is not advisable.
Because fuel tends to get dirty in transport, storage tanks, and from debris
that builds up in the tank, a 10 micron filter before the pump will
inadvertently become plugged and stop flowing, which is a danger to the engine.
And since the fuel pump itself can slough off material (particularly during the
break-in period) it is always necessary to run a 10 micron filter after the
pump to protect the injectors.

What If I Need More HP Than One Pump Can Feed?

Hey, it happens. Two days before writing this I spoke with a fellow who
needed two 450 LPH and one 255 LPH pump to run this psycho Corvette he built.
If you find yourself needing more than one pump then contact us and we can build
you a custom kit.